Polishing pad and polishing device

ABSTRACT

The present invention relates to a polishing pad which is characterized in that it has a polishing layer of rubber A-type microhardness at least 80° and a cushioning layer of bulk modulus at least 40 MPa and tensile modulus in the range 0.1 MPa to 20 MPa, and to a polishing device which is characterized in that a semiconductor substrate is fixed to the polishing head, and an aforesaid polishing pad is fixed to the polishing platen so that the polishing layer faces the semiconductor substrate, and by rotating the aforesaid polishing head or the polishing platen, or both, the semiconductor substrate is polished. 
     With the polishing device or polishing pad of the present invention for use in the mechanical planarizing process wherein the surface of the insulating layers or metal interconnects formed on a semiconductor substrate are smoothened, it is possible to uniformly planarize the entire semiconductor face and perform uniform polishing close up to the wafer edge and, furthermore, it is possible to provide a technique for achieving both uniformity and planarity under conditions of high platen rotation rate.

TECHNICAL FIELD

The present invention relates to a semiconductor substrate polishingdevice and polishing pad; more particularly, it relates to a polishingdevice and a polishing pad for the mechanical planarization of thesurface of insulating layers and the surface of metal interconnectsformed on a silicon or other semiconductor substrate.

TECHNICAL BACKGROUND

Year by year, there are ever greater levels of integration in largescale integrated circuits (LSI) typified by semiconductor memories and,along with this, large scale integrated circuit production technology isproviding ever greater packaging densities. Moreover, together with suchincreasingly high densities, the number of semiconductor device layersis also increasing. As a result of this increase in the number oflayers, while not hitherto being an issue, the unevenness in thesemiconductor wafer main face produced by such layering has become aproblem. For example, as described in Nikkei Microdevice, July 1994,pages 50-57, the planarization of the semiconductor wafer using chemicalmechanical polishing (CMC) techniques is being investigated with theobjective of dealing with the inadequate depth of focus at the time oflight exposure due to the unevenness produced by layering, or with theobjective of raising interconnect densities by planarizing through-holeregions.

Generally speaking, CMP equipment is composed of a polishing head forholding the semiconductor substrate, which is the material undergoingtreatment, a polishing pad for carrying out polishing of the materialundergoing treatment, and a polishing platen for holding this polishingpad. In the semiconductor substrate polishing treatment, a slurrycomprising polishing agent and chemical liquid is used and, by effectingrelative motion between the semiconductor substrate and the polishingpad, the semiconductor substrate surface layer is smoothened. In thecase, for example, of a silicon dioxide (SiO₂) film formed on a mainface of the semiconductor substrate, the polishing rate at the time ofthis semiconductor substrate polishing process is roughly proportionalto the relative velocity between semiconductor substrate and polishingpad, and the load. Hence, in order to bring about uniform polishing ofeach region of the semiconductor substrate, it is necessary to make theload applied to the semiconductor substrate uniform.

However, there are often variations in level over the entire surface ofthe semiconductor substrate held on the polishing head, due to inherentcurvatures and other such variations in shape. Hence, it is desirablethat there be used a soft polishing pad in order to apply a uniform loadto each region of the semiconductor substrate. However, when a polishingprocess is carried out using a soft polishing pad, the planarity of thesemiconductor substrate surface local unevenness is impaired. Forexample, the problem arises that in parts unevenness of the aforesaidsemiconductor substrate surface layer is rounded by the polishing, thatis to say the polished face is rounded and not made planar. In contrast,in the case where the polishing of the semiconductor substrate iscarried out in the same way using a hard polishing pad then, while it ispossible to enhance the planarity of the semiconductor substrate surfacelocal unevenness unlike in the case of using a soft polishing pad, thehard polishing pad is unsatisfactory from the point of view of adaptingto overall variations in level at the semiconductor substrate. Forexample, uneven regions of the semiconductor substrate surface whereundulations project outwards are considerably polished, but unevenregions where such undulations are depressed are largely unpolished andremain as they are. Such non-uniform polishing leads to exposure of thealuminium interconnects and local variations in the thickness of thesilicon dioxide insulating film following polishing and, for example,through-hole diameter irregularities and the fact that planarization ofunevenness due to layer superposition is not possible, cause inadequatedepth of focus at the time of light exposure.

With regard to the prior-art relating to polishing pads aimed atsatisfying the opposing demands of enhancing such local planarity andoverall adaptability, a two layer pad has been tried as described inJP-A-6-21028. The two layer pad described in JP-A-6-21028 has aconstruction where the polishing layer which directly contacts thesemiconductor substrate is supported on a cushioning layer of bulkmodulus no more than 250 psi/psi within the stress range 4 psi to 20psi, and the polishing layer has a bulk modulus greater than this. Theobjective is that the cushioning layer absorbs overall variations inlevel on the semiconductor substrate, while the polishing layer isresistant to curvature over more than a certain area (for example morethan the die spacing). However, with this conventional two-layer pad,the following problems still remain in terms of polishing performance.Firstly, even though the bulk modulus of the polishing layer is greaterthan the bulk modulus of the cushioning layer, the local planarity ofthe semiconductor substrate surface may still be impaired, and there isnot necessarily a correlation between local planarity and the bulkmodulus of the polishing layer. Secondly, since the bulk modulus of thecushioning layer is no more than 250 psi/psi within the stress range 4psi to 20 psi, there is poor adaptability to variations in level overthe semiconductor substrate as a whole, with the result that there isnot obtained sufficient uniformity of planarity over the entire face ofthe semiconductor substrate. Furthermore, as stated on pages 177-183 ofCMP Science by Science Forum Publishing (Co.), it has not been possibleto fully resolve the question of how close to the edge within the waferface is the required planarization to be carried out. Thirdly, if therate of rotation of the polishing platen is high, the planarity is goodbut there is the problem that adaptability to the variations in levelover the entire semiconductor substrate face is made worse.Consequently, an improved polishing device or polishing pad is requiredto overcome the above problems.

DISCLOSURE OF THE INVENTION

The objective of the present invention lies in offering a means foruniformly planarizing the entire face of a semiconductor substrate, inthe case of a polishing device or a polishing pad employed in amechanical planarizing process in which the surface of insulating layersor metal interconnects formed on a semiconductor substrate aresmoothened by polishing. Specifically, this invention relates to “apolishing pad which is characterized in that it has a polishing layer ofrubber A-type microhardness of at least 80° and a cushioning layer ofbulk modulus at least 40 MPa and tensile modulus in the range 0.1 MPa to20 MPa”

and

“a method of polishing a semiconductor substrate which is characterizedin that the semiconductor substrate is fixed to a polishing head, andthe semiconductor substrate is polished by rotating said polishing heador a polishing platen, or both, in a state where there is pressedagainst the semiconductor substrate a polishing layer of rubber A-typemicrohardness at least 80° affixed to the polishing platen via acushioning layer of bulk modulus at least 40 MPa and tensile modulus 0.1MPa to 20 MPa”

and also

“a polishing device which is characterized in that it is a polishingdevice equipped with a polishing head, a polishing pad which confrontsthe polishing head, a polishing platen to which the polishing pad isfixed, and a means for rotating the polishing head, the polishing platenor both of these, and where the polishing pad contains a cushioninglayer of bulk modulus at least 40 MPa and tensile modulus in the range0.1 to 20 MPa and, in the direction of the polishing head, a polishinglayer of rubber A-type microhardness at least 80° ”.

OPTIMUM MODE FOR PRACTISING THE INVENTION

Below, the mode of practising the invention is explained. The cushioninglayer in the present invention needs to have a bulk modulus of at least40 MPa and a tensile modulus in the range 0.1 MPa to 20 MPa. Preferably,the bulk modulus of the cushioning layer is at least 60 MPa and morepreferably at least 90 MPa, and the preferred tensile modulus is 0.5 MPato 18 MPa, and more preferably the tensile modulus is 5 MPa to 15 MPa.The bulk modulus is determined by applying an isotropic impressedpressure on the material subject to measurement, the volume of which haspreviously been measured, and then measuring the resulting change involume. The bulk modulus is defined by the relation bulkmodulus=impressed pressure/(change in volume/original volume). Forexample, if the original volume is 1 cm³, and the volume change when animpressed pressure of 0.07 MPa is isotropically applied thereto is0.00005 cm³, then the bulk modulus is 1400 MPa. As an example of onemethod for measuring the bulk modulus, there is the method where thevolume of the material undergoing measurement is first determined, afterwhich said material undergoing measurement is immersed in water within acontainer, then this container introduced into a pressure vessel andpressure applied, and measurement made of the impressed pressure and thechange in the volume of the material undergoing measurement based on thechange in the height of the water in the container. With regard to theimmersion liquid, it is preferred that there be avoided liquids whichswell or damage the material undergoing measurement, but otherwise thereare no particular restrictions on the liquid and examples are water,mercury, silicone oil and the like. The tensile modulus is determined byforming a dumbbell shape from the cushioning layer and applying atensile stress thereto. The tensile stress is measured in the range oftensile strain (=change in length/original length) 0.01 to 0.03, and thetensile modulus is defined by the relation tensile modulus=((tensilestress at a tensile strain of 0.03)−(tensile stress at a tensile strainof 0.01))/0.02. As an example of the measurement instrument, there isthe Tensilon general-purpose testing machine RTM-100 made by theOrientec Co. With regard to the measurement conditions, there isemployed a testing rate of 5 cm/minute, and the test-piece shape is thatof a dumbbell of width 5 mm and sample length 50 mm.

It is necessary that the bulk modulus of the cushioning layer be atleast 40 MPa. If it is less than 40 MPa, then the uniformity of theplanarity of the semiconductor substrate face as a whole is impaired, sothis is undesirable. Furthermore, the tensile modulus of the cushioninglayer needs to be in the range from 0.1 MPa to 20 MPa. If is less than0.1 MPa, then the uniformity of the planarity of the semiconductorsubstrate face as a whole is impaired, so this is undesirable. If itexceeds 20 MPa, then again the uniformity of the planarity of thesemiconductor substrate face as a whole is impaired, so this isundesirable. Examples of such a cushioning layer are unfoamed elastomerslike natural rubber, nitrile rubber, neoprene rubber, polybutadienerubber, polyurethane rubber and silicone rubber, but there are noparticular restrictions thereto. The preferred thickness of thecushioning layer lies in the range 0.1 to 100 mm. If it is less than 0.1mm, then the uniformity of the planarity of the semiconductor substrateface as a whole is impaired, so this is undesirable. If it exceeds 100mm, then the local planarity is impaired, which is undesirable. Thethickness range 0.2 to 5 mm is further preferred and 0.5 to 2 mm stillfurther preferred. Next, explanation will be given of the rubber A-typemicrohardness referred to in the present invention. The rubber A-typemicrohardness denotes the value determined by means of a rubbermicrodurometer. This instrument is supplied by the Kobunshi Keiki Co.,as rubber microdurometer model MD-1. With rubber microdurometer MD-1 itis possible to measure the hardness of small/thin samples which has beendifficult to measure by conventional durometers. Since it has beendesigned and produced at abut ⅕^(th) the scale of the spring-systemrubber durometer model A, the measured value obtained is a value whichcorresponds to the spring-system rubber durometer A-type hardness. Inthe case of an ordinary polishing pad, the polishing layer or hard layerthickness is cut to 5 mm, so it is too thin for the spring-system rubberdurometer model A and evaluation is not possible, but evaluation ispossible with the rubber microdurometer MD-1.

The polishing layer of the polishing pad of the present invention is apolishing layer of rubber A-type microhardness at least 80°. The rubberA-type microhardness needs to be at least 80° but is preferably at least90°. If the rubber A-type microhardness is less than 80°, the globalplanarity of the semiconductor substrate local unevenness is poor, sothis is undesirable. The tensile modulus of the cushioning layer of thepolishing pad relating to the present invention is determined by forminga dumbbell shape of the polishing layer and applying a tensile stressthereto. The tensile stress is measured in the range of tensile strain(=change in length/original length) 0.01 to 0.03, and the tensilemodulus is defined by the relation tensile modulus=((tensile stress at atensile strain of 0.03)−(tensile stress at a tensile strain of0.01))/0.02. As an example of the measurement instrument used, there isthe Tensilon general-purpose testing machine RTM-100 made by theOrientec Co. With regard to the measurement conditions, there isemployed a testing rate of 5 cm/minute, and the test-piece shape is thatof a dumbbell of width 5 mm and sample length 50 mm. Where the polishinglayer possesses closed cells, there is high polishing agent retentionand the polishing rate is raised, so this is preferred. With regard tothe closed cell diameter, where the average cell diameter is no morethan 1000 μm there is excellent planarity of the semiconductor substratelocal unevenness, so this is preferred. It is further preferred in termsof the closed cell diameter that the average cell diameter be no morethan 500 μm and still more preferably no more than 300 μm.

It is preferred that the chief component of the polishing layer bepolyurethane and that the density lies in the rang 0.7 to 0.9. If thedensity is less than 0.7, the polishing rate is lowered, which isundesirable. If the density exceeds 0.9, the polishing rate is lowered,which is undesirable. A still further preferred polishing layer containspolyurethane and a polymer obtained by polymerization of a vinylcompound where the content of this polymer obtained by polymerization ofa vinyl compound is from 50 wt % to 90 wt %, and which has closed cellsof average cell diameter no more than 1000 μm and a density of 0.4 to1.1. This polyurethane is a polymer synthesized based on apolyisocyanate polyaddition or polymerization reaction. The compoundemployed to react with the polyisocyanate is a compound containingactive hydrogens, that is to say a polyhydroxy or amino group-containingcompound with two or more active hydrogens. Examples of thepolyisocyanate are tolylene diisocyanate, diphenylmethane diisocyanate,naphthalene diisocyanate, tolidine diisocyanate, hexamethylenediisocyanate and isophorone diisocyanate, but there is no restriction tothese. Polyhydroxy compounds are typified by polyols, and as examples ofpolyols there are polyether-polyols, polyoxytetramethylene glycol, epoxyresin-modified polyols, polyester-polyols, acrylic polyols,polybutadiene polyols, silicone polyols and the like.

Vinyl compound in the present invention means a compound with apolymerizable carbon-carbon double bond. Specific examples are methylmethacrylate, ethyl methacrylate, propyl methacrylate, n-butylmethacrylate, isobutyl methacrylate, methyl (α-ethyl)acrylate, ethyl(α-ethyl)acrylate, propyl (α-ethyl)acrylate, butyl (α-ethyl)acrylate,2-ethylhexyl methacrylate, isodecyl methacrylate, n-lauryl methacrylate,2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate,2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 2-hydroxybutylmethacrylate, dimethylaminoethyl methacrylate, diethylaminoethylmethacrylate, methacrylic acid, glycidyl methacrylate, ethylene glycoldimethacrylate, fumaric acid, dimethyl fumarate, diethyl fumarate,dipropyl fumarate, maleic acid, dimethyl maleate, diethyl maleate,dipropyl maleate, acrylonitrile, acrylamide, vinyl chloride, styrene,α-methylstyrene and the like. Of these, preferred vinyl compounds aremethyl methacrylate, ethyl methacrylate, propyl methacrylate, n-butylmethacrylate, isobutyl methacrylate, methyl (α-ethyl)acrylate, ethyl(α-ethyl)acrylate, propyl (α-ethyl)acrylate and butyl( α-ethyl)acrylate.Specifically, there are methyl methacrylate, ethyl methacrylate, n-butylmethacrylate, isobutyl methacrylate, 2-ethylhexyl methacrylate, isodecylmethacrylate, n-lauryl methacrylate, 2-hydroxyethyl methacrylate,2-hydroxypropyl methacrylate, 2-hydroxyethyl acrylate, 2-hydroxypropylacrylate, 2-hydroxybutyl methacrylate, dimethylaminoethyl methacrylate,diethylaminoethyl methacrylate, methacrylic acid, glycidyl methacrylate,ethylene glycol dimethacrylate, fumaric acid, dimethyl fumarate, diethylfumarate, dipropyl fumarate, maleic acid, dimethyl maleate, diethylmaleate, dipropyl maleate, acrylonitrile, acrylamide, vinyl chloride,styrene, α-methylstyrene and the like. Of these, preferred vinylcompounds are methyl methacrylate, ethyl methacrylate, propylmethacrylate, n-butyl methacrylate, isobutyl methacrylate, methyl(α-ethyl)acrylate, -ethyl (α-ethyl)acrylate, propyl (α-ethyl)acrylateand butyl (α-ethyl)acrylate. The aforesaid preferred vinyl compoundsreadily impregnate polyurethanes and, when polymerization is carried outwithin the polyurethane, there is obtained a polishing layer of highhardness and high toughness, and so they are preferred. As examples ofthe polymers derived from the polymerization of the vinyl compound inthe present invention, there are polymethyl methacrylate, polyethylmethacrylate, polypropyl methacrylate, poly(n-butyl methacrylate),polyisobutyl methacrylate, polymethyl (α-ethyl)acrylate, polyethyl(α-ethyl)acrylate, polypropyl (α-ethyl)acrylate, polybutyl(α-ethyl)acrylate, poly(2-ethylhexyl methacrylate), polyisodecylmethacrylate, poly(n-lauryl methacrylate), poly(2-hydroxyethylmethacrylate), poly(2-hydroxypropyl methacrylate), poly(2-hydroxyethylacrylate), poly(2-hydroxypropyl acrylate), poly(2-hydroxybutylmethacrylate), polydimethylaminoethyl methacrylate,polydiethylaminoethyl methacrylate, polymethacrylic acid, polyglycidylmethacrylate, polyethylene glycol dimethacrylate, polyfumaric acid,polydimethyl fumarate, polydiethyl fumarate, polydipropyl fumarate,polymaleic acid, polydimethyl maleate, polydiethyl maleate, polydipropylmaleate, polyacrylonitrile, polyacrylamide, polyvinyl chloride,polystyrene, poly(α-methylstyrene) and the like. Of these, as preferredpolymers, polymethyl methacrylate, polyethyl methacrylate, polypropylmethacrylate, poly(n-butyl methacrylate), polyisobutyl methacrylate,polymethyl (α-ethyl)acrylate, polyethyl (α-ethyl)acrylate, polypropyl(α-ethyl)acrylate and polybutyl (α-ethyl)acrylate can raise the hardnessof the polishing pad and the planarization characteristics can beimproved. It is preferred that the content of the polymer obtained bypolymerization of the vinyl compound in the present invention be atleast 50 wt % and up to 90 wt %. If the content of the polymer derivedfrom the vinyl monomer is less than 50 wt %, the hardness of thepolishing layer will be lowered, so this is undesirable. If the amountexceeds 90 wt %, the elasticity of the polishing layer is impaired, sothis is undesirable.

With regard to the method of producing the polishing layer of thepresent invention, a preferred method is the method in which a foamedpolyurethane sheet having closed cells of average cell diameter no morethan 1000 μm and having a density in the range 0.1 to 1.0, is swollenbeforehand with the vinyl compound, after which polymerization of thevinyl compound is carried out within the foamed polyurethane sheet. Inthis way, it is possible to produce a polishing layer containing bothpolyurethane with a closed cell structure and polymer derived from thevinyl compound. Of course, it is necessary to determine the combinationand optimum amounts of polyisocyanate, polyol, catalyst, foam regulatorand foaming agent in accordance with the target polishing layerhardness, cell diameter and density.

As examples of the method employed for polymerizing the vinyl compoundwithin the foamed polyurethane sheet following the swelling of thefoamed polyurethane sheet by means of the vinyl compound, there are themethod of carrying out the swelling with a vinyl compound together witha photo radical initiator and then bringing about polymerization byexposure to light, the method of carrying out the swelling with a vinylcompound together with a thermal radical initiator and then bringingabout polymerization by application of heat, and the method of carryingout the swelling with a vinyl compound and then bringing aboutpolymerization by exposure to an electron beam or to radiation.

In the present invention, affixing the polishing layer to the polishingplaten via a cushioning layer, refers to fixing in such a way that thecushioning layer does not slip from the polishing platen at the time ofpolishing and, furthermore, fixing in such a way that the polishinglayer does not slip from the cushioning layer. As the method for fixingtogether the cushioning layer and the polishing platen, there may beconsidered the method of fixing with double-sided adhesive tape, themethod of fixing with an adhesive agent or the method of applyingsuction from the polishing platen to fix the cushioning layer, but thereis no particular restriction on the method used. As the method forfixing the polishing layer to the cushioning layer, there may beconsidered the method of fixing with double-sided adhesive tape or themethod of fixing with an adhesive agent, but there is no particularrestriction on the method used. Double-sided tape or an adhesive agentlayer can be used as an intermediate layer for coupling together thepolishing layer and the cushioning layer. It is preferred that thetensile modulus of this double-sided adhesive tape or adhesive layer beno more than 20 MPa. The tensile modulus of double-sided adhesive tapeis determined by forming a dumbbell shape and applying a tensile stressthereto. The tensile stress is measured in the range of tensile strain(=change in length/original length) 0.01 to 0.03, and the tensilemodulus is defined by the relation tensile modulus=((tensile stress at atensile strain of 0.03)−(tensile stress at a tensile strain of0.01))/0.02. The tensile modulus of the adhesive layer is determined byfirst producing a laminate by application of the adhesive layer betweentwo sheets of rubber of known tensile modulus, then producing a dumbbellshape and performing an evaluation of the tensile modulus, after whichthere is applied the formula ((tensile modulus of thelaminate)×(thickness of the laminate)−2×(tensile modulus of therubber)×(thickness of one sheet of rubber))÷(thickness of the adhesivelayer). As an example of the measurement instrument, there is theTensilon general-purpose testing machine RTM-100 produced by theOrientec Co. With regard to the measurement conditions, there isemployed a testing rate of 5 cm/minute, and the test-piece shape is thatof a dumbbell of width 5 mm and sample length 50 mm. If the tensilemodulus of the intermediate layer exceeds 20 MPa, the uniformity withinthe face is impaired, so this is undesirable.

Preferred specific examples of the double-sided adhesive tape oradhesive layer for sticking together the polishing layer and thecushioning layer are Sumitomo 3M (Ltd) double-sided adhesive tapes 463,465 and 9204, Nitto Denko (Corp.) double-sided adhesive tape No.591 andother such substrate-free acrylic adhesive transfer tapes, double-sidedadhesive tape with a foamed sheet substrate such as Y-4913 produced bySumitomo 3M (Ltd), and double-sided adhesive tape with a nonrigid vinylchloride substrate such as 447DL produced by Sumitomo 3M (Ltd).

With the polishing device in the present invention, in cases where, forreasons such as the polishing rate not being realized, it is necessaryto replace the polishing layer after polishing, it is also possible toremove the polishing layer from the cushioning layer and to replace itwhile the cushioning layer remains fixed to the polishing platen. Thecushioning layer is durable when compared to the polishing layer, soreplacing just the polishing layer is advantageous in terms of cost.

Below, the method of polishing a semiconductor substrate using thepolishing pad according to the present invention is explained.

It is possible to planarize unevenness on the semiconductor substrateinsulating films or metal interconnects using the polishing pad of thepresent invention by employing for example a silica-based polishingagent, an aluminium oxide based polishing agent or a cerium oxide basedpolishing agent as the polishing agent. Firstly, there is prepared thepolishing device which is equipped with a polishing head, a polishingplaten for fixing the polishing pad, and a means for effecting rotationof the polishing head, the polishing platen or both. Then, the polishingpad of the present invention is affixed to the polishing platen of thepolishing device in such a way that the polishing layer confronts thepolishing head. The semiconductor substrate is fixed by a method such asa vacuum chuck to the polishing head. The polishing platen is made torotate, and the polishing head is made to rotate in the same directionas the polishing platen and pressed against the polishing pad. At thistime, polishing agent is supplied between the polishing pad and thesemiconductor substrate from a position such that polishing agent can beintroduced. Normally, the pressing pressure is controlled by the forceapplied to the polishing head. Where this is in the range 0.01 to 0.2MPa, local planarity is obtained, so this is preferred.

By means of the polishing device and polishing pad of the presentinvention, it is possible to achieve uniformity in terms of theplanarity of the local unevenness over the entire face of thesemiconductor substrate, and it is possible to achieve uniform polishingclose up to the wafer edge. Furthermore, it is possible to achieve bothuniformity and planarity under conditions of high platen rotation rate.

EXAMPLES

Below, the details of the present invention are further explained alongwith examples. In these examples, the various properties were measuredby the following methods.

1. Rubber A-type Microhardness:

Measurement was carried out with a Kobunshi Keiki (Co.) [address:Shimodachiuri Muromachi Nishiiri, Kamigyo-ku, Kyoto] rubbermicrodurometer MD-1.

The structure of the rubber microdurometer MD-1 was as follows.

1.1 Sensor Region

(1) Loading system: cantilever plate spring type

(2) Spring load:  0 point  2.24 gf 100 point 33.85 gf

(3) Spring load error: ±0.32 gf

(4) Indenter dimensions: diam: 0.16 mm circular cylinder height  0.5 mm

(5) Displacement detection system: strain gauge

(6) Pressure foot dimensions: outer diameter   4 mm inner diameter 1.5mm

1.2 Sensor Driving Region

(1) Driving system: vertically driven based on a stepping motor,descending rate control based on an air damper

(2) Vertical stroke: 12 mm

(3) Rate of descent: 10-30 mm/sec

(4) Height adjustment range: 0 to 67 mm (distance between sample tableand sensor pressure face)

1.3 Sample Stand

(1) Sample stand dimension: diameter 80 mm

(2) Fine adjustment mechanism: fine adjustment based on XY table andmicrometer head; stroke for both X and Y axes=15 mm

(3) Level adjustment means: main feet for level adjustment and roundspirit level

2. Global Step Height

(1) Test Wafer

A 20 mm square die was arranged on a 6-inch silicon wafer. On the lefthalf of this 20 mm square die, there were provided aluminiuminterconnects of width 40 μm and height 1.2 μm, at a spacing of 40 μm,in line-and-space fashion, and on the right half there were providedaluminium interconnects of width 400 μm and height 1.2 μm, at a spacingof 40 μm, in line-and-space fashion. Furthermore, on top thereof, aninsulating film of 3 μm thickness was formed by CVD usingtetraethoxysilane, to prepare the test wafer for evaluation of theglobal step height.

(2) Evaluation Method

Evaluation Conditions A

The test wafer for evaluation of the global step height was fitted tothe polishing head of the polishing machine and made to rotate at 37rpm. The composite polishing pad was fixed to the polishing machineplaten and made to rotate at 36 rpm in the same direction as thedirection of rotation of the polishing head. While supplying asilica-based polishing agent at 200 ml/minute, polishing was carried outfor a specified time at a polishing pressure of 0.05 MPa. The globalstep height between the 40 μm width and 400 μm width interconnectregions of the global step height evaluation test wafer was measured.

Evaluation Conditions B

The test wafer for evaluation of the global step height was fitted tothe polishing head of the polishing machine and made to rotate at 47rpm. The composite polishing pad was fixed to the polishing machineplaten and made to rotate at 46 rpm in the same direction as thedirection of rotation of the polishing head. While supplying asilica-based polishing agent at 200 ml/minute, polishing was carried outfor a specified time at a polishing pressure of 0.05 MPa. The globalstep height between the 40 μm width and 400 μm width interconnectregions of the global step height evaluation test wafer was measured.

3. OXIDE FILM REMOVAL RATE

(1) Test Wafer

A 1.2 μm thermally-oxidized film was formed on a 6-inch test wafer, toproduce the test wafer for evaluation of the oxide film removal rate.

(2) Evaluation Method

Evaluation Conditions C

The test wafer for evaluation of the oxide film removal rate was fittedto the polishing head of the polishing machine and made to rotate at 37rpm, and the polishing pad was affixed to the polishing machine platenand made to rotate at 36 rpm in the same direction as the direction ofrotation of the polishing head. While supplying a silica-based polishingagent at 225 ml/minute, polishing was carried out for 3 minutes at apolishing pressure of 0.05 MPa. The oxide film removal rate was measuredat 1 mm spacings within 5 mm of the wafer edge, and the average oxidefilm removal rate and the uniformity within 5 mm of the wafer edge whereuniformity=(maximum oxide removal rate−minimum oxide removalrate)÷2÷average oxide removal rate×100, were calculated. Furthermore,the oxide film removal rate was measured at 1 mm spacings within 3 mm ofthe wafer edge, and the average oxide film removal rate and theuniformity within 3 mm of the wafer edge where uniformity=(maximum oxideremoval rate−minimum oxide removal rate)÷2÷average oxide removalrate×100, were calculated.

Evaluation Conditions D

The test wafer for evaluation of the oxide film removal rate was fittedto the polishing head of the polishing machine and made to rotate at 47rpm, and the polishing pad was affixed to the polishing machine platenand made to rotate at 46 rpm in the same direction as the direction ofrotation of the polishing head. While supplying a silica-based polishingagent at 225 ml/minute, polishing was carried out for 3 minutes at apolishing pressure of 0.05 MPa. The oxide film removal rate was measuredat 1 mm spacings within 5 mm of the wafer edge, and the average oxidefilm removal rate and the uniformity within 5 mm of the wafer edge whereuniformity=(maximum oxide removal rate−minimum oxide removalrate)÷2÷average oxide removal rate×100, were calculated. Furthermore,the oxide film removal rate was measured at 1 mm spacings within 3 mm ofthe wafer edge, and the average oxide film removal rate and theuniformity within 3 mm of the wafer edge where uniformity=(maximum oxideremoval rate−minimum oxide removal rate)÷2÷average oxide removalrate×100, were calculated.

Example 1

A foamed polyurethane sheet (rubber A-type microhardness=50°, density:0.77 and average diameter of closed cells: 110 μm) of thickness 5 mm wasimmersed for 24 hours in methyl methacrylate to which 0.1 part by weightof azobisisobutyronitrile had been added. The foamed polyurethane sheetwhich had been swollen by the methyl methacrylate was then interposedbetween glass plates and heated for 24 hours at 70° C. After heating, itwas removed from the glass plates and dried under vacuum at 50° C. Itwas then subjected to grinding and a polishing layer of thickness 1.2 mmobtained. The rubber A-type microhardness of this polishing layer was98°, density: 0.79, average diameter of closed cells: 150 μm, and theproportion by weight of polymethyl methacrylate was 69 wt %. A polishingpad was produced by sticking together this polishing layer and a 1 mmnitrile rubber (bulk modulus=140 MPa, tensile modulus=4.5 MPa)cushioning layer with Nitto Denko double-sided adhesive tape No.591(tensile modulus no more than 0.1 MPa). Using a silica-type polishingagent, the evaluation of the oxide film removal rate was carried outunder evaluation conditions C at a platen rotation rate of 36 rpm. Theaverage oxide film removal rate within 5 mm of the wafer edge was 1020Å/minute and the uniformity 8, and the average oxide film removal ratewithin 3 mm of the wafer edge was 1050 Å/minute and the uniformity 10.Furthermore, when evaluation conditions D were used at a platen rotationrate of 46 rpm, the average oxide film removal rate within 5 mm of thewafer edge was 1340 Å/minute and the uniformity 7, while the averageoxide film removal rate within 3 mm of the wafer edge was 1350 Å/minuteand the uniformity 11. When an evaluation was carried out of the globalstep height under evaluation conditions A at a platen rotation rate of36 rpm for a polishing time of 2 minutes, the global step height betweenthe 40 μm width and 400 μm width interconnect regions of the global stepheight evaluation test wafer was 0.04 μm. Again, when the global stepheight was evaluated under evaluation conditions B at a platen rotationrate of 46 rpm for a polishing time of 1 minute 45 seconds, the globalstep height between the 40 μm width and 400 μm width interconnectregions of the global step height evaluation test wafer was 0.01 μm.

Example 2

30 parts by weight of polypropylene glycol, 40 parts by weight ofdiphenylmethane diisocyanate, 0.8 parts by weight of water, 0.3 parts byweight of triethylamine, 1.7 parts by weight of silicone foam stabilizerand 0.09 parts by weight of tin octylate were mixed together in an RIMmoulding machine, discharged into a mould and subjected to pressuremoulding, to produce a foamed polyurethane sheet (rubber A-typemicrohardness=50°, density: 0.51 and average diameter of closed cells:40 μm) of thickness 1.5 mm. This foamed polyurethane sheet was immersedfor 15 hours in methyl methacrylate to which 0.1 part by weight ofazobisisobutyronitrile had been added. The foamed polyurethane sheetwhich had been swollen by the methyl methacrylate was interposed betweenglass plates and heated for 24 hours at 70° C. After heating, it wasremoved from the glass plates and dried under vacuum at 50° C. The hardfoamed sheet obtained was then subjected to grinding at both faces and a1.2 mm polishing pad obtained. The rubber A-type microhardness of thispolishing pad was 980, density: 0.75, average diameter of closed cells:60 μm and the polymethyl methacrylate content of the polishing pad was82 wt %. 2 mm polyurethane rubber (bulk modulus=100 MPa, tensilemodulus=10 MPa) was prepared as a cushioning layer, and a polishing padwas produced by sticking together the polishing layer and the cushioninglayer with Sumitomo 3M (Ltd) double-sided adhesive tape #950 (tensilemodulus no more than 0.1 Mpa). Using a silica-type polishing agent, theevaluation of the oxide film removal rate was carried out underevaluation conditions C at a platen rotation rate of 36 rpm. The averageoxide film removal rate within 5 mm of the wafer edge was 1210 Å/minuteand the uniformity 7, and the average oxide film removal rate within 3mm of the wafer edge was 1230 Å/minute and the uniformity 10.Furthermore, when evaluation conditions D were used at a platen rotationrate of 46 rpm, the average oxide film removal rate within 5 mm of thewafer edge was 1540 Å/minute and the uniformity 9, and the average oxidefilm removal rate within 3 mm of the wafer edge was 1560 Å/minute andthe uniformity 11. When an evaluation was carried out of the global stepheight under evaluation conditions A at a platen rotation rate of 36 rpmfor a polishing time of 1 minute 45 seconds, the global step heightbetween the 40 μm width and 400 μm width interconnect regions of theglobal step height evaluation test wafer was 0.04 μm. Again, when theglobal step height was evaluated under evaluation conditions B at aplaten rotation rate of 46 rpm for a polishing time of 1 minute 30seconds, the global step height between the 40 μm width and 400 μm widthinterconnect regions of the global step height evaluation test wafer was0.02 μm.

Example 3

78 parts by weight of a polyether-based -urethane polymer (AdipreneL-325, produced by Uniroyal), 20 parts by weight of4,4′-methylene-bis2-chloroaniline and 1.8 parts by weight of hollowpolymer microspheres (Expancel 551 DE produced by the Chema-Nobel Co.)were mixed together in an RIM moulding machine, and discharged into amould to produce a moulded polymer body. This moulded polymer body wassliced to a thickness of 1.2 mm with a slicer, to produce the polishinglayer. The rubber A-type microhardness of this polishing layer was 980,density: 0.80, average diameter of closed cells: 33 μm. 1 mm neoprenerubber (bulk modulus=100 MPa, tensile modulus=12 MPa) was prepared as acushioning layer, and a polishing pad was produced by sticking togetherthe polishing layer and the cushioning layer with Sumitomo 3M (Ltd)double-sided adhesive tape Y-949 (tensile modulus 10 Mpa). Using asilica-type polishing agent, the evaluation of the oxide film removalrate was carried out under evaluation conditions C at a platen rotationrate of 36 rpm. The average oxide film removal rate within 5 mm of thewafer edge was 1110 Å/minute and the uniformity 6, and the average oxidefilm removal rate within 3 mm of the wafer edge was 1130 Å/minute andthe uniformity 10. Furthermore, when evaluation conditions D were usedat a platen rotation rate of 46 rpm, the average oxide film removal ratewithin 5 mm of the wafer edge was 1340 Å/minute and the uniformity 9,and the average oxide film removal rate within 3 mm of the wafer edgewas 1360 Å/minute and the uniformity 11. When an evaluation was carriedout of the global step height under evaluation conditions A at a platenrotation rate of 36 rpm for a polishing time of 2 minutes, the globalstep height between the 40 μm width and 400 μm width interconnectregions of the global step height evaluation test wafer was 0.06 μm.Again, when the global step height was evaluated under evaluationconditions B at a platen rotation rate of 46 rpm for a polishing time of1 minute 45 seconds, the global step height between the 40 μm width and400 μm width interconnect regions of the global step height evaluationtest wafer was 0.04 μm.

Example 4

The polishing layer employed in Example 1 was used. A polishing pad wasproduced by sticking a 1.5 mm chloroprene rubber (bulk modulus=80 MPa,tensile modulus=10 MPa) cushioning layer to this polishing layer withNitto Denko double-sided adhesive tape No.591 (tensile modulus no morethan 0.1 Mpa). Using a silica-type polishing agent, the evaluation ofthe oxide film removal rate was carried out under evaluation conditionsC at a platen rotation rate of 36 rpm. The average oxide film removalrate within 5 mm of the wafer edge was 1030 Å/minute and the uniformity8, and the average oxide film removal rate within 3 mm of the wafer edgewas 1060 Å/minute and the uniformity 10. Furthermore, when evaluationconditions D were used at a platen rotation rate of 46 rpm, the averageoxide film removal rate within 5 mm of the wafer edge was 1310 Å/minuteand the uniformity 10, and the average oxide film removal rate within 3mm of the wafer edge was 1360 Å/minute and the uniformity 12. When anevaluation was carried out of the global step height under evaluationconditions A at a platen rotation rate of 36 rpm for a polishing time of2 minutes, the global step height between the 40 μm width and 400 μmwidth interconnect regions of the global step height evaluation testwafer was 0.04 μm. Again, when the global step height was evaluatedunder evaluation conditions B at a platen rotation rate of 46 rpm for apolishing time of 1 minute 45 seconds, the global step height betweenthe 40 μm width and 400 μm width interconnect regions of the global stepheight evaluation test wafer was 0.01 μm.

Example 5

The polishing layer employed in Example 1 was used. A polishing pad wasproduced by sticking a 1 mm chloroprene rubber (bulk modulus=50 MPa,tensile modulus=11 MPa) cushioning layer to this polishing layer withNitto Denko double-sided adhesive tape No.591 (tensile modulus no morethan 0.1 Mpa). Using a silica-type polishing agent, the evaluation ofthe oxide film removal rate was carried out under evaluation conditionsC at a platen rotation rate of 36 rpm. The average oxide film removalrate within 5 mm of the wafer edge was 1050 Å/minute and the uniformity7, and the average oxide film removal rate within 3 mm of the wafer edgewas 1070 Å/minute and the uniformity 11. Furthermore, when evaluationconditions D were used at a platen rotation rate of 46 rpm, the averageoxide film removal rate within 5 mm of the wafer edge was 1370 Å/minuteand the uniformity 11, and the average oxide film removal rate within 3mm of the wafer edge was 1350 Å/minute and the uniformity 14. When anevaluation was carried out of the global step height under evaluationconditions A at a platen rotation rate of 36 rpm for a polishing time of2 minutes, the global step height between the 40 μm width and 400 μmwidth interconnect regions of the global step height evaluation testwafer was 0.04 μm. Again, when the global step height was evaluatedunder evaluation conditions B at a platen rotation rate of 46 rpm for apolishing time of 1 minute 45 seconds, the global step height betweenthe 40 μm width and 400 μm width interconnect regions of the global stepheight evaluation test wafer was 0.01 μm.

Example 6

The polishing layer employed in Example 1 was used. A polishing pad wasproduced by sticking a 0.5 mm ethylene-propylene rubber (bulkmodulus=100 MPa, tensile modulus 19 MPa) cushioning layer to thispolishing layer with Nitto Denko double-sided adhesive tape No.591(tensile modulus no more than 0.1 Mpa). Using a silica-type polishingagent, the evaluation of the oxide film removal rate was carried outunder evaluation conditions C at a platen rotation rate of 36 rpm. Theaverage oxide film removal rate within 5 mm of the wafer edge was 1000Å/minute and the uniformity 6, and the average oxide film removal ratewithin 3 mm of the wafer edge was 960 Å/minute and the uniformity 10.Furthermore, when evaluation conditions D were used at a platen rotationrate of 46 rpm, the average oxide film removal rate within 5 mm of thewafer edge was 1270 Å/minute and the uniformity 10, and the averageoxide film removal rate within 3 mm of the wafer edge was 1290 Å/minuteand the uniformity 12. When an evaluation was carried out of the globalstep height under evaluation conditions A at a platen rotation rate of36 rpm for a polishing time of 2 minutes, the global step height betweenthe 40 μm width and 400 μm width interconnect regions of the global stepheight evaluation test wafer was 0.04 μm. Again, when the global stepheight was evaluated under evaluation conditions B at a platen rotationrate of 46 rpm for a polishing time of 1 minute 45 seconds, the globalstep height between the 40 μm width and 400 μm width interconnectregions of the global step height evaluation test wafer was 0.01 μm.

Example 7

The polishing layer employed in Example 1 was used. A polishing pad wasproduced by sticking a 1.5 mm ethylene-propylene rubber (bulkmodulus=110 MPa, tensile modulus=16 MPa) cushioning layer to thispolishing layer with Nitto Denko double-sided adhesive tape No.591(tensile modulus no more than 0.1 Mpa). Using a silica-type polishingagent, the evaluation of the oxide film removal rate was carried outunder evaluation conditions C at a platen rotation rate of 36 rpm. Theaverage oxide film removal rate within 5 mm of the wafer edge was 990Å/minute and the uniformity 7, and the average oxide film removal ratewithin 3 mm of the wafer edge was 1000 Å/minute and the uniformity 11.Furthermore, when evaluation conditions D were used at a platen rotationrate of 46 rpm, the average oxide film removal rate within 5 mm of thewafer edge was 1370 Å/minute and the uniformity 12, and the averageoxide film removal rate within 3 mm of the wafer edge was 1390 Å/minuteand the uniformity 14. When an evaluation was carried out of the globalstep height under evaluation conditions A at a platen rotation rate of36 rpm for a polishing time of 2 minutes, the global step height betweenthe 40 μm width and the 400 μm width interconnect regions of the globalstep height evaluation test wafer was 0.04 μm. Again, when the globalstep height was evaluated under evaluation conditions B at a platenrotation rate of 46 rpm for a polishing time of 1 minute 45 seconds, theglobal step height between the 40 μm width and 400 μm width interconnectregions of the global step height evaluation test wafer was 0.01 μm.

Example 8

The polishing layer employed in Example 1 was used. A polishing pad wasproduced by sticking a 1.5 mm silicone rubber (bulk modulus=120 MPa,tensile modulus=0.7 MPa) cushioning layer to this polishing layer withNitto Denko double-sided adhesive tape No.591 (tensile modulus no morethan 0.1 Mpa). Using a silica-type polishing agent, the evaluation ofthe oxide film removal rate was carried out under evaluation conditionsC at a platen rotation rate of 36 rpm. The average oxide film removalrate within 5 mm of the wafer edge was 1100 Å/minute and the uniformity7, and the average oxide film removal rate within 3 mm of the wafer edgewas 1130 Å/minute and the uniformity 11. Furthermore, when evaluationconditions D were used at a platen rotation rate of 46 rpm, the averageoxide film removal rate within 5 mm of the wafer edge was 1330 Å/minuteand the uniformity 9, and the average oxide film removal rate within 3mm of the wafer edge was 1370 Å/minute and the uniformity 12. When anevaluation was carried out of the global step height under evaluationconditions A at a platen rotation rate of 36 rpm for a polishing time of2 minutes, the global step height between the 40 μm width and the 400 μmwidth interconnect regions of the global step height evaluation testwafer was 0.04 μm. Again, when the global step height was evaluatedunder evaluation conditions B at a platen rotation rate of 46 rpm for apolishing time of 1 minute 45 seconds, the global step height betweenthe 40 μm width and 400 μm width interconnect regions of the global stepheight evaluation test wafer was 0.01 μm.

Comparative Example 1

The polishing layer employed in Example 3 was prepared. The rubberA-type microhardness of the polishing layer was 98°, density: 0.80 andthe average diameter of closed cells: 33 μm. As the cushioning layer,there was prepared a wet-foamed polyurethane (bulk modulus=3 MPa,tensile modulus=50 MPa) of thickness 1.2 mm obtained by wet filmformation following impregnation of a nonwoven material with apolyurethane solution. A polishing pad was produced by sticking togetherthe polishing layer and the cushioning layer with Sumitomo 3M (Ltd)double-sided adhesive tape 442J (a double-sided adhesive tape in whichthe substrate is polyester film; tensile modulus=200 MPa). Using asilica-type polishing agent, the evaluation of the oxide film removalrate was carried out under evaluation conditions C at a platen rotationrate of 36 rpm. The average oxide film removal rate within 5 mm of thewafer edge was 1150 Å/minute and the uniformity 10, and the averageoxide film removal rate within 3 mm of the wafer edge was 1130 Å/minuteand the uniformity 17. Furthermore, when evaluation conditions D wereused at a platen rotation rate of 46 rpm, the average oxide film removalrate within 5 mm of the wafer edge was 1370 Å/minute and the uniformity17, and the average oxide film removal rate within 3 mm of the waferedge was 1360 Å/minute and the uniformity 20. Thus, the uniformity waspoor. When an evaluation was carried out of the global step height underevaluation conditions A at a platen rotation rate of 36 rpm for apolishing time of 2 minutes, the global step height between the 40 μmwidth and 400 μm width interconnect regions of the global step heightevaluation test wafer was 0.06 μm. Again, when the global step heightwas evaluated under evaluation conditions B at a platen rotation rate of46 rpm for a polishing time of 1 minute 45 seconds, the global stepheight between the 40 μm width and 400 μm width interconnect regions ofthe global step height evaluation test wafer was 0.04 μm.

Comparative Example 2

There was produced a polishing layer of foamed polyurethane obtained bywet film formation following impregnation of a nonwoven materialcomprising polyester fibre (fibre diameter 6 μm) with a polyurethanesolution. The rubber A-type microhardness of this polishing layer was75°. As the cushioning layer, there was prepared a wet-foamedpolyurethane (bulk modulus=3 MPa, tensile modulus=50 MPa) of thickness1.2 mm, which was obtained by wet film formation following impregnationof a nonwoven material with a polyurethane solution. A polishing pad wasproduced by sticking together this polishing layer and cushioning layerwith Sumitomo 3M (Ltd) double-sided adhesive tape 442J (double-sidedadhesive tape in which the substrate is polyester film; tensilemodulus=200 MPa). Using a silica-type polishing agent, the evaluation ofthe oxide film removal rate was carried out under evaluation conditionsC at a platen rotation rate of 36 rpm. The average oxide film removalrate within 5 mm of the wafer edge was 850 Å/minute and the uniformity6, and the average oxide film removal rate within 3 mm of the wafer edgewas 890 Å/minute and the uniformity 7. Furthermore, when evaluationconditions D were used at a platen rotation rate of 46 rpm, the averageoxide film removal rate within 5 mm of the wafer edge was 1010 Å/minuteand the uniformity 6, and the average oxide film removal rate within 3mm of the wafer edge was 1050 Å/minute and the uniformity 8. When anevaluation was carried out of the global step height under evaluationconditions A at a platen rotation rate of 36 rpm for a polishing time of2 minutes, the global step height between the 40 μm width and the 400 μmwidth interconnect regions of the global step height evaluation testwafer was 0.15 μm. Again, when the global step height was evaluatedunder evaluation conditions B at a platen rotation rate of 46 rpm for apolishing time of 1 minute 45 seconds, the global step height betweenthe 40 μm width and 400 μm width interconnect regions of the global stepheight evaluation test wafer was 0.10 μm. Thus, the global step heightwas poor.

Comparative Example 3

The polishing layer employed in Example 3 was prepared. The rubberA-type microhardness of the polishing layer was 98°, density: 0.80 andthe average diameter of the closed cells: 33 μm. As the cushioninglayer, there was prepared a 1 mm sheet of polybutylene terephthalate(bulk modulus=600 MPa, tensile modulus=100 MPa). A polishing pad wasproduced by sticking together this polishing layer and cushioning layerwith Sumitomo 3M (Ltd) double-sided adhesive tape Y-949 (tensile modulus10 MPa). Using a silica-type polishing agent, the evaluation of theoxide film removal rate was carried out under evaluation conditions C ata platen rotation rate of 36 rpm. The average oxide film removal ratewithin 5 mm of the wafer edge was 1150 Å/minute and the uniformity 20,and the average oxide film removal rate within 3 mm of the wafer edgewas 1130 Å/minute and the uniformity 25. Furthermore, when evaluationconditions D were used at a platen rotation rate of 46 rpm, the averageoxide film removal rate within 5 mm of the wafer edge was 1370 Å/minuteand the uniformity 21, while the average oxide film removal rate within3 mm of the wafer edge was 1360 Å/minute and the uniformity 23. Thus theuniformity was poor. When an evaluation was carried out of the globalstep height under evaluation conditions A at a platen rotation rate of36 rpm for a polishing time of 2 minutes, the global step height betweenthe 40 μm width and 400 μm width interconnect regions of the global stepheight evaluation test wafer was 0.06 μm. Again, when the global stepheight was evaluated under evaluation conditions B at a platen rotationrate of 46 rpm for a polishing time of 1 minute 45 seconds, the globalstep height between the 40 μm width and 400 μm width interconnectregions of the global step height evaluation test wafer was 0.04 μm.

Comparative Example 4

The polishing layer employed in Example 3 was prepared. As thecushioning layer, there was prepared 1 mm neoprene rubber (bulkmodulus=100 MPa, tensile modulus=12 MPa), and a polishing pad wasproduced by sticking together the polishing layer and cushioning layerwith Sumitomo 3M (Ltd) double-sided adhesive tape 442J (double-sidedadhesive tape in which the substrate is polyester film; tensilemodulus=200 MPa). Using a silica-type polishing agent, the evaluation ofthe oxide film removal rate was carried out under evaluation conditionsC at a platen rotation rate of 36 rpm. The average oxide film removalrate within 5 mm of the wafer edge was 1110 Å/minute and the uniformity20, and the average oxide film removal rate within 3 mm of the waferedge was 1130 Å/minute and the uniformity 25. Furthermore, whenevaluation conditions D were used at a platen rotation rate of 46 rpm,the average oxide film removal rate within 5 mm of the wafer edge was1340 Å/minute and the uniformity 21, while the average oxide filmremoval rate within 3 mm of the wafer edge was 1360 Å/minute and theuniformity 24. Thus the uniformity was poor. When an evaluation wascarried out of the global step height under evaluation conditions A at aplaten rotation rate of 36 rpm for a polishing time of 2 minutes, theglobal step height between the 40 μm width and the 400 μm widthinterconnect regions of the global step height evaluation test wafer was0.06 μm. Again, when global step height was evaluated under evaluationconditions B at a platen rotation rate of 46 rpm for a polishing time of1 minute 45 seconds, the global step height between the 40 μm width and400 μm width interconnect regions of the global step height evaluationtest wafer was 0.04 μm.

TABLE 1 Polishing Pad Construction Polishing Characteristics RubberUniformity A-type Tensile Evaluation Evaluation Micro- Cushioning LayerModulus of Conditions C Conditions D Hardness of Bulk TensileIntermediate within within within within Global Step Height (μm)Polishing Modulus Modulus Layer 5 mm of 3 mm of 5 mm of 3 mm ofEvaluation Evaluation Layer (MPa) (MPa) (MPa) edge edge edge edgeConditions A Conditions B Example 1 98 140 4.5 ≦0.1 8 10 7 11 0.04 0.01Example 2 98 100 10 ≦0.1 7 10 9 11 0.04 0.02 Example 3 98 100 12 10 6 109 11 0.06 0.04 Example 4 98 80 10 ≦0.1 8 10 10 12 0.04 0.01 Example 5 9850 11 ≦0.1 7 11 11 14 0.04 0.01 Example 6 98 100 19 ≦0.01 6 10 10 120.04 0.01 Example 7 98 110 16 ≦0.1 7 11 12 14 0.04 0.01 Example 8 98 1200.7 ≦0.1 7 11 9 12 0.04 0.01 Comp. Ex. 1 98 3 50 200 10 17 17 20 0.060.04 Comp. Ex. 2 75 3 50 200 6 7 6 8 0.15 0.10 Comp. Ex. 3 98 600 100 1020 25 21 23 0.06 0.04 Comp. Ex. 4 98 100 12 200 20 25 21 24 0.06 0.04

What is claimed is:
 1. A polishing pad which is characterized in that ithas a polishing layer of rubber A-type microhardness of at least 80° anda cushioning layer of bulk modulus at least 40 MPa and tensile modulusin the range 0.1 MPa to 20 MPa.
 2. A polishing pad according to claim 1which is characterized in that the bulk modulus of the cushioning layeris at least 60 MPa.
 3. A polishing pad according to claim 2 which ischaracterized in that the bulk modulus of the cushioning layer is atleast 90 MPa.
 4. A polishing pad according to claim 1 which ischaracterized in that the tensile modulus of the cushioning layer is inthe range 0.5 MPa to 18 MPa.
 5. A polishing pad according to claim 4which is characterized in that the tensile modulus of the cushioninglayer is in the range 5 MPa to 15 MPa.
 6. A polishing pad according toclaim 1 which is characterized in that the thickness of the cushioninglayer is in the range 0.1 to 100 mm.
 7. A polishing pad according toclaim 6 which is characterized in that the thickness of the cushioninglayer is in the range 0.2 to 5 mm.
 8. A polishing pad according to claim1 which is characterized in that the chief component of the polishinglayer is polyurethane and, furthermore, the density is in the range 0.70to 0.90.
 9. A polishing pad according to claim 1 which is characterizedin that the polishing layer contains polyurethane and polymer from thepolymerization of a vinyl compound and the proportion of polymer fromthe polymerization of a vinyl compound is 50-90 wt %, and it possessesclosed cells of average cell diameter no more than 1000 μm and,furthermore, the density is in the range 0.4 to 1.1.
 10. A polishing padaccording to claim 1 which is characterized in that the tensile modulusof an intermediate layer between the polishing layer and the cushioninglayer is no more than 20 MPa.
 11. A method of polishing a semiconductorsubstrate which is characterized in that the semiconductor substrate isfixed to a polishing head and, with a polishing pad according to claim 1fixed to a polishing platen in a state such that the polishing layer ispressed against the semiconductor substrate, said semiconductorsubstrate is polished by rotation of the aforesaid polishing head orpolishing platen, or both.
 12. A polishing method according to claim 11which is 30 characterized in that the polishing pad is a polishing padaccording to claim
 9. 13. A polishing device which is characterized inthat it is a polishing device equipped with a polishing head, apolishing pad confronting the polishing head, a polishing platen towhich the polishing pad is fixed, and a means for rotating the polishinghead, the polishing platen or both of these, and where the polishing padis the polishing pad according to claim 1, the polishing layer of whichis fixed and faces the polishing head.
 14. A polishing device accordingto claim 13 where the polishing head has a means for fixing thesemiconductor substrate.